AFAIK mutation observers are not available yet in IE. Chrome, Safari, Firefox have their implementations and its working its way through the standardization process. I'm wondering if anyone (preferably MS employee) knows the story with IE, or might give me a pointer to an article I missed.
IE 11 supports MutationObservers
natively. For IE 9-10 you can use this polyfill:
https://github.com/Polymer/MutationObservers